mediation analysis in lavaan with binary outcome and continuous mediator

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Mar 14, 2019, 5:10:32 PM3/14/19
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Hi Yves,
I have used lavaan in the past for SEM based mediation analysis. Initially both my outcome and mediator variables were continuous, where things are straightforward. Recently, I have been working with a binary outcome, and I am confused about the validity of this analysis. The basic method for mediation analysis is based on the two regression equations (Baron and Kenny):
mediator = a*treatment + error
outcome = b*mediator + c*treatment + error
where the indirect effect (a*b) can be estimated by the product of coefficients method. Now if the outcome is binary, then we replace the linear model above with logit or probit regression. In this case, work by Imai et al. (see attached paper, page 773) argues that the product of coefficients method is no longer valid (the estimate of a*b is not asymptotically consistent) using the sequential ignorability assumption.  Does this mean that SEM in lavaan with a binary outcome, a continuous mediator and a discrete treatment does not produce valid results? I know that SEM has been extended to discrete endogenous variables, but this extension has not specifically considered mediation analysis. So is mediation analysis with a continuous mediator and a binary outcome, estimating the indirect effect a*b, valid?
Thanks, Ina


Terrence Jorgensen

Mar 21, 2019, 6:42:07 AM3/21/19
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This is not a software question, more appropriate for SEMNET

Terrence D. Jorgensen
Assistant Professor, Methods and Statistics
Research Institute for Child Development and Education, the University of Amsterdam

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